1. Field of the Invention
The present invention relates to a backlight for a color liquid crystal display apparatus, and specifically relates to a form of backlight that allows three colors of light (R (red), G (green), B (blue)) from a light source to impinge directly on the corresponding pixels of a liquid crystal display panel without passing through a color filter.
2. Description of the Related Art
Along with the development of liquid crystal technology in recent years, liquid crystal display (LCD) modules that use backlights with a light emitting diode (LED) as a light source are being implemented. In most LED backlights, LED light of three colors is mixed in a light guide to become white light, and is combined with a color filter to display color. However, there are problems such as the brightness fading when using a color filter.
In order to improve this problem, Japanese Laid-Open Patent Application No. 2002-196332 discloses a color liquid crystal display apparatus provided with an LED backlight wherein LED light of three colors directly enters the corresponding pixels of the LCD, the light intensity is controlled with a liquid crystal shutter, and color is displayed without using a color filter.
FIG. 1 is a schematic diagram that shows a conventional LED backlight according to FIG. 3 of Japanese Laid-Open Patent Application No. 2002-196332. Light from a red LED 111 is introduced into a light guide 101. Light emitted from a pit or other deformed part 120 passes through a polarizing filter 104 and is incident on a color pixel sequence that corresponds to a TFT (Thin Film Transistor) array 105, as shown in FIG. 1. Similarly, light from a blue LED 112 is introduced into a light guide 102. Light emitted from a deformed part 120 is incident on the color pixel sequence of the corresponding TFT array 105. Light from a green LED 113 also enters a light guide 103 and is incident on the corresponding color pixel sequence of the TFT array 105 from the deformed part 120. Each light guide 101, 102, and 103 therefore has a layered construction.
Conventionally, in order to simultaneously introduce the three colors of light from an LED light source into an LCD panel, the components are aligned and the three light-guide plates superposed on each other so that the light from the each R, G, and B LED light source was directed to the three separate light-guide plates and the light of each color enters the corresponding pixels of the LCD panel, with the three plates stacked up. Therefore, with conventional LED backlights, aligning and superposing each of the three light-guide plates was necessary in order to coordinate the corresponding color pixels of the LCD panel with the light-guide plate thereof. The size of an LCD panel pixel that corresponds to one color is about 100 μm×300 μm, and three pixels lined up have a size of about 300 μm×300 μm. Each pixel displays a single color, and a darkened band having a width of about 15 μm is forms between the pixels. Therefore, an accurate superposition was necessary to obtain the 15 μm width of the darkened band in each light-guide plate and LCD panel, and manufacture was extremely difficult.